Holy Water is a thrown item that transforms the blocks it hits into Hallow. It can be used as a weapon, dealing around 20 damage to most enemies. A more practical use is removing Corruption or The Crimson.02:35

Holy Water Terraria HERO

Contents

Uses

Holy water is an effective method of removing The Corruption/Crimson , arguably more so than Purification Powder because the latter reverts corruption to neutral stone/grass/sand, which will shortly become corrupt again, especially when playing in Hard Mode. Holy water on the other hand Hallows whatever it touches, meaning these areas will stay cleansed for a much longer period of time. However, if the aim of cleansing the Corruption was to make it more liveable, remember that the Monsters found in the Hallow are equally as deadly as those of the Corruption.

Holy water can be taken to worlds in which the Wall of Flesh has not yet been killed; they can be a very effective way of removing Corruption on such worlds. However, on these worlds, given the slow nature and limitations of the Corruption's spread (it being stopped by Sunflowers or small amounts of artificial blocks) it may be easier to use Purification Powder instead.

Another possible limitation of Holy Water is the materials required: gathering Pixie Dust takes time, and Hallowed Seeds can be expensive when bought in bulk.

As mentioned at the top of the article, Holy Water can be used as a weapon, although it deals little damage. The only time this could be useful is when battling enemies in the area you're trying to Hallow.

Unholy Water has an equal and opposite effect to Holy Water, spreading Corruption instead of Hallow.

Notes

When thrown from high heights (around 500 ft above ground) the bottle reaches its maximum travel capacity and suddenly explodes, doing no purifying.

Prior from 1.2, Holy Water was the best way to remove the corruption, but after the 1.2 update, the Clentaminator removes any biome a lot quicker (The whole screen in only 2-3 seconds.) than the Holy Water.

Trivia

Holy Water may be a reference to Castlevania's Holy Water weapon. Early American versions of Castlevania were often censored to remove references to religious materials and the holy water weapon was referred to as a Fire Bomb.